Telephone-exchange system



Sept. 15, 1925. 1,553,347

. S. B. WILLIAMS TELEPHONE EXQHANGE SYSTEM Filed Aug. 17, 1923 14 Sheets-Sheet 1 hvenfor: Sam'ue/ B. VVf/fiams.

y M A Sept. 15, 1925.

S B WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed A .17. 1925 14 Sheets-Sheet 2 hven/bn Samue/ B. l V/flidms Sept. 15, 1925.

S. B..WILL|AM$ TELEPHO NE EXCHANGE SYSTEM Filed g. 1'7, 1923 14 sheets-Sheet s mn/enfon- Sahwe/ 5. Wflfiams.

Sept. 15, 1925.

S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Rug. 1'7, 1923 14 Sheets-Sheet 4 Sept. 15, 1925.

S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Fil Aug- 17. 192-3 l4 SheQtS-ShGGi 5 fivven/ar- Samue/ 5. l V/fl/dms. 9 f

Sept. 15, 1925.

mw 3 a 0 e r M by Q Q 9% @5. 1 a w NE m% w M% M m a wm 5% w Q Q Qw LKQ S B WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed A Sept. 15, 1925. 1,553,347

s. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed A 1'7. 1923 14 Sheets-Sheet 7 Q i x R mven/orby W X my Spt. 15, 1925.

S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Aug. 17, 1923 l4 Sheets-Sheet 8 m M M W v 5 m a W M g. a S b \\N\\ A\\\ Nh was QR fiNw Sept. 15, 1925.

5. B. VVILLEAMS TELEPHONE EXCHANGE SYSTEM iled Aug. 1.7 1923 Sept. 15, 1925.

S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed M 17, 192:5

l4 Shets-Sheet 10 Sept. 15, 1925.

S. B. WILLIAMS TELEPHONE EXCHANGE SYS TEM QQ QR Filed Aug. 17, 1923 Sept. 15,1925. 1,553,347

S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Aug. 1'7, 1923 14 Sheets-Sheet 12 //7l /7/0/: Samue/ 5. [MW/4M5.

k WW I Sept. 15, 1925.

1 Sheets-Sheet 13 Ynven/or: Sdmue/ 5. l W/fidms.

S B WILLIAMS TELEPHONE EXCHANGE SY STEM Filed Aug. 1'7, 1923 Sept. 15", 1925.

S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Aug. 1 1923 14 Sheets-Sheet 14 Patented Sept. 15, 1925.

UNITED STATES PATENT OFFICE.

SAMUEL IB. WILLIAMS, OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed August 17, 1923. Serial No. 657,839.

To all whom it may concern Be it known that I, SAMUEL B. WILLIAMS, a citizen of the United States of America, residin at Brooklyn, in the county of Kings and S tate of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to sys tems involving machine switching apparatus for the establishment of conversational connections.

The object of this invention is an improved telephone system wherein the selective switches, which serve to establish con-' nections of different classes, are under the control of the same selection controlling mechanism. a

A feature of the invention relates to a system wherein calls extended automatically and calls extended by operators are further extended by automatic switches under the control of a register sender mechanism which may receive its records either over the automatically extended connections or from the operators positions.

Another feature relates to a register con- I trolling sender which is adapted to receive code impulses sent either from another reg ister sender or from an operators position for the purpose of controlling selective switches. l

A further feature relates to a system hav ing incoming trunks from automatic offices and trunks from operators positions and a sender selector for associating senders with any of these trunks, together with means for sending records either over the incoming trunks from the automatic offices or from the operators positions through said sender selector to the senders.

Other features and advantages contemplated by the invention will be taken up in detail hereinafter and pointedout in the appended claims.

Considering the drawing, Figs. 1 to 14:, inclusive, taken in the order illustrated in Fig. 15 disclose the details of a telephone system incorporating the features of the present invention.

Fig. 1 shows a trunk circuit incoming to tlfifie central office from a distant mechanical 0 cc.

Fig. 2 illustrates an incoming selector switch of the coordinate type in which terminate trunks incoming form the mechanical office.

Fig. 3 shows a second group selector switch to which connections are extended from the incoming switch in Fig. 2.

Fig. 4 illustrates a final or connector switch of the coordinate type employed for completing connections to the called subscribers lines.

Fig. 5 shows a coordinate sender selector switch serving to extend the incoming trunks into connection with one of the number of register sender mechanisms.

Figs. 6, 7 and 8 illustrate details of one of the register senders. Figs. 7 and 8 constitute the relay registers of the sender upon which the designation records are estabhshcd.

Fig. 9 shows a sender connector, deviceconsisting of multicontactrelays for associating the senders with the incoming marker together with certain control relays.

Fig. 10 shows the incoming marker mechanism which controls a plurality of incoming selectors to which it is common and associable.

][n the lower part of Fig. 11 there is illustrated a multicontact relay sender connector device for connecting the senders with the line marker. 7

In the remainder of Fig. 11 and in Fig. 12 there is shown the line marker which is associable with the group selectors and connectors of Figs. 3 and 4 for controlling these switches to complete connections.

Fig. 13 discloses an operators keyboard and impulse sending mechanism located in the same office with the switches shown in Figs. 2, 3 and 4. v

Fig. 14 shows a trunk circuit incoming to the operators position from a distant office which trunk terminates in the incoming selector switch of Fig. 2 together with the other trunks incoming from the distant mechanical offices.

There is disclosed in the drawings illustrating this invention a terminating central office to which connections of different types are extended for completion to called subscribcrs lines therein. This ofiice is arranged to cooperate with distant full mechanical oiiices, one of which is illustrated diagrammatically at the left of Fig. 1. The connections after being extended from the mechanical ofiice by means of automatic switches to the terminating otiice here represented appear first in incoming selector switches shown in Fig. 2. Following the extension of the connection to the incoming selector switch an idle register sender is associated with the incoming trunk and receives the record by means of code impulses which are transmitted over the incoming trunk from the automatic sending mechanism in the distant mechanical oiiice.

After the record is established on the sender the markers are attached to the sender in the proper order and control the switches in the terminating office to complete the connection to the desired line.

Calls of another type handled by the terminating otlice are those originating in distant manual oflices, for instance, and destined for some subscribers line in the terminating oilice which can only be reached through the medium of the automatic selector switches. To attend to this type of service the terminating office is equipped with cordless operators positions at which keyboards are installed for setting up the records pertaining to the called lines.

The incoming trunks from the manual originating offices terminate 1n any suitable manner in the same incoming automatlc switches with the trunks above mentioned which arrive from the mechanical ofiices. These incoming trunks are under the control and supervision of the cordless operators,

whose duty it is to make the necessary assignments orally to the distant operators and bring about release at the proper times. The cordless operators, on receiving the designations orally, set them up on a keyboard with the result that these records are transferred by code impulses from the operators position to the same register senders which are employedin connection withcalls originated or extended from the full mechanicalotlices. I

' According to the aforegoing outline of the arrangement of the apparatus in the termimting oilice a number of register sender mechanisms and marker controlling devices are placed at the universal disposal of connections of a full mechanical nature and also of connections which are partially es'' tablished through the medium of operators. Another desirable advantage is that with the particular type of switching medium employed for completing the connections in the terminating ofiice, the varying" types of incoming trunks, including those from mechanical oflices and those from manual offices,

are distributed in the same switching mech- General description of the system and apparatus.

The selective switches including the incoming selectors 200, group selectors 300, connectors 400, sender selectors 500 and the other selector switches employed in this system are. of the coordinate type such as shown and described in the patent to S. B. Williams No. 1,517,331, issued December 2, 1924.

The trunk 100 incoming from the mechanical oflice to the terminating otiice appears in the vertical row of contacts 202 of the incoming selector switch 200 and has access to all horizontal links 205, 206, etc. This incoming selector is shown in schematic form, only a limited number of the vertical rows of contacts and a limited number of the horizontal links being illustrated. It should be understood, of course, that this switch may have any desired capacity. The incoming trunk 1 100 from the distant manual oflice also appears in the same incoming switch 200 in the vertical row of contacts 201, likewise, having access to all horizontal links. In a similar manner other trunks incoming from ditl'erent otfices would appear in this and other equivalent incoming selector switches. I

The incoming selector switch 200 also has a plurality of groups of outgoing trunks appearing in rows 203, 20 etc. Each outgoing trunk is shown having an appearance before a single horizontal link such as the links 205, 206. These trunks are multipled in order to appear before corresponding horizontal links in allot the remaining incoming selector switches controlled by the same marker mechanism. The trunks outgoing from the incoming selector switch are distributed among the different group selectors 300, one of these trunks 211 being shown in full.

A convenient manner of arranging the "likewise comprise a proper number of group selector and connector switches and a line marker for controlling said switches. According to this plan the trunks outgoing from the incoming switches 200 would be distributed among the group selectors 300 in each of the five terminal line groups in order that any one of the ten thousand lines n'iight be accessible.

Considering the terminal line group, the group selectors 300 are equipped with a number of groups of outgoing trunks wlnch lead to thevarious conncctor switches 400 of that particular group. One such trunk 319 is illustrated in full.

The called subscribers lines appear in the connector switches in groups. For instance, each of the vertical rows 417 and 418 represents a groin.) of subscribers lines. Each line is accessible over a group of horizontal links. The line 416 appears in the group occupying the vertical row 41S and is accessible by a group of links, two of which 401 and 402 are shown. A second line 426 in the same group is accessible to another group of horizontal links 404 and 405. Similarly, other lines in the same row (not shown in the disclosure) would be accessible to other groups of horizontal links. Each group of horizontal links is provided with a common test link for the purpose of testing the condition of the called lines to which that group of links has access. The common test link 403 serves with respect to the group of horizontal links containing the links 401 and 402. to the second group ofhorizontal links shown. As will be seen hereinafter." these 7 test links are onlyoperated for a brief in terval at the proper time when conditions are favorable to make a test of the called subscribers line.

The incoming marker shown in .FigtflO includes a series of testing relays 1000 which serve to test the horizontal links in any of the incoming selector switches to which this marker is common and also to test the outgoing trunks which have access to those horizontal links. The connecting device 1002 which comprisesa number of. multicontact relays 1004, 1005, 1006, 1007, etc. serves to connect the set of test relays 1000 with the proper group of outgoing trunks,

the multicontact relays each being indivual to a different group. Also a connecting device 1001 consisting of multicont-act relays 1008,1009, 1010, 1020, 1021, 1022, etc. serves to connect the marker testing relays with the individual incoming switches. Relays 1008, 1009, and 1010, for instance, are in dividual to the particular incoming switch 200 illustrated in the drawing. Similarly, relays 1020, 1021 and 1022 are individual to a second incoming switch (not shown).

The linemarker shown in Figs. 11 and 12 includes a plurality of registers 1200. 1201, and 1202 which receive numerical records from the controlling sender. It also includes the multicontact relay translating The'link 406 likewise is common.

device 1204 which is operated according to the settings of the registers to select the magnets 414, 415 individual to the diii'erent vertical rows of outgoing lines in the connector switches. Moreover the line marker includes a n'iulticontact relay translating device 1203 which operates to associate the register 1201 with a connecting device 410 individual to the proper connector switch 400. The device 410 consisting ofv relays 411, 412, etc. serves to associate certain test relays with the horizontal links of the group having access to the called lines of the desired units designation. In Fig. 11 a set of testing relays of the marker are shown and these relays are associable, through the mnlticontact relay connecting device 301 and 302 with the groups of trunks outgoing from the selector switch 400 and other switches and also with the horizontal links of these group selectors.

The sender selector switches 500 comprise a plurality of rows of contacts 501, 502, etc. together with horizontal links 505, 507 and 508. These horizontal links are arranged in groups, one group being represented by the single link 505 and another group being illustrated by the two links 507 and 508.

"The trunks incoming from the distant offices each appear in the sender selector switches as illustrated. Thetrunk 100, for instance, incoming from themechanical oilice appears inthe vertical row 501 and before all horizontal links belonging to the particular group which contains the lint 505, trunk 1400 incoming from the distant manual The oflice also appears in the vertical row 501 and before all horizontal links of the group containing the links 507 and 508. In'wany torswitches.

In addition the sender selector 500 has a number of rows of contacts 503, 504, etc, in each of which appears a circuit leading to a .register sender. The circuit 532, for inzontal links in all groups A second circuit similar and suitable fashion other trunks 533 is illustrated which leads to another' equipped with certain impulse generating.

mechanism whereby code impulses are originated in accordance'with the record on the keyboard and transmitted through the sender selector switch 500 to the associated register sender in order to record upon such sender,

Detailed description of the systeme8tab- Zishment of a full mechanical connection.

Consider that a connection is extended from a distant mechanical oflice illustrated at the left of Fig. 1 over a trunk 100 to the terminating oflice. Assume, also that the party originating this call desires to converse with the subscriber of line 416 in the terminatin office and that the number of this called e is 1 3 2 6. In any well-known manner the connection is extended over automatic switches such as the switch 110 in the originating mechanical office by way of the interoifice trunk 100 to the incoming selector switch 200 in the terminating oflice.

-Upon the extension of the connection over the trunk 100 a circuit is closed from battery, through the left-hand winding of relay 104, left normal contact of rela 103, upper left winding of repeating coil 101, outer right back contact of relay 102, thence over the tip of the trunk 100, through a closed bridge at the mechanical oifice and returning over the ring of trunk 100, inner right back contact of relay 102, lower left-hand winding of coil 101, right normal contact of relay 103, right-hand winding of relay 104 to ground. Relay 104 operates and closes a circuit from ground through its contact through the winding of relay 107. Relay 107 closes a circuit from ground over conductor 115, back contact of relay 106, conductor 114, inner left back contact of relay 102, winding of relay 513 to battery.

Relay 513 operates and a circult is completed from battery through the winding of relay 515, right back contact of relay 514, conductor 535, inner right contact of relay 513, conductor 536, winding ofrelay 537 to ground.

Relays 514, 515 and 516 enclosed within the broken rectangle pertain to the vertical group of contacts in the row 501 in the switch 500. These relays are brought into action whenever one of the trunks a pearing in this row is seeking to be attac ed to one of the register senders.

Relay 515 completes a circuit from battery through the winding of relay 519, left contact of relay 515, conductor 536, to ground through the winding of relay 537. Relay 515 also closes a circuit from battery through the left-hand winding of relay 516, right front contact of relay 515, left back contact of relay 517, outer right contact of relay 523 to ground through the winding of relay 537 Relay 516 at its outer left contact closes a circuit for relay 514. Relay 514 locks in a circuit through its winding and left contact, left front contact of relay 519 to ground at the contact of slow release relay 520.- Relay 516 also closes a circuit from battery through its right winding and right contact, winding of relay 517, outer right contact of relay 523 to ground through the winding of relay 537. Relay 517 operates and closes a circuit from battery through the winding of slow-to-release relay 522, outer right contact of relay 517, inner right back contact of relay 523 to ground through. the winding of relay 537. Relay 522 closes a substitute holding circuit for relays 516 and 517 independent of the relay 523.

With relay 517 operated a circuit is closed from battery through the winding of the vertical operating magnet 529, outer right front contact of relay 516, left front contact of relay 517, outer rightcontact of relay "523 to ground through the winding of relay 537. The magnet 529 operates and prepares the contacts of the vertical row 501. Magnet 529 also closes a circuit from ground through its contact, conductor 552, left contact of relay 521, inner left contact of relay 516, outer right contact of relay 513, lefthand winding of relay 512 to battery. Relay 512 is a group relay individual to the group of horizontal links including the link 505. Similarly, relay 538 is a group relay individual to the group of links containing the links 507 and 508.

Relay 512 operates and closes a circuit from battery through its right-hand winding and right contact, right back contact of relay 538, assuming the relay 538 to be deenergized at this time, winding of relay 521, conductor 552, to ground, at the contact of magnet 529, Relay 521 operates in this circuit.

Another circuit is closed from battery through the winding of the vertical operating magnet 531, brush 527 of the allotter 526, contact of slow release relay 525, left energize.

540, brush 528 of the allotter switch, contact and winding of the stepping magnet 524,

through the winding of relay 525 to bat-- tery. The magnet 524 operates, interrupts its own circuit and advances the brushes 527 and 528'to the next set. of terminals. If the following sender is idle, the allotter switch comes to rest, but if it is busy the switch continues until an idle sender is found. When the switch leaves the position shown, it opens the shunt around the relay 523 and this relay operates in series with magnet 531. The relay 523 opens the circuit of relay 522 which commences to de- The relay 522 being slowholds its armatures for an interval after the operation of relay 523 which is sufficient for certain operations to take place as will be presently described.

During the interval measured by the re lease of relay 522, a circuit is closed from ground through the winding of relay 537, inner right front contact of relay 523, right contact of relay 521, left back contact of relay 538, left front contact of relay 512, back contact of relay 509, winding of the horizontal operating magnet 510, individual to the link 505, to battery; The magnet 510 operates and effects a connection between the link 505 and the incoming circuit and also between the link and the outgoing circuit 532.

At the time the vertical operating magnet 531 operates a circuit is closed from ground through the outer contact of said magnet, conductor 540, inner left back contact of relay 605, winding of slow-to-release relay 600 to battery. Relay 600 operates and closes a circuit for relay 605. Relay 600 also looks in a circuit from battery through its winding and right contact, conductor 637, outer left contact of .relay 638,

outer left back contact of relay 632, conductor 639, outermost right contact of. relay 604, inner right cont-act of relay 605 to ground at the left front contact of relay Immediately that the connection is established through the sender selector switch 500 a circuit is closed from battery to the winding of the horizontal magnet 510, winding of relay 509, contacts of the switch 500, conduct-or 540, inner left front contact of relay 605, winding of relay 601 to ground at the inner left contact of relay 603. The magnet 510 is, hel nerg zed in this circuit under the control of the sender after the above traced energizing circuit has been opened. Relay 509, however, being shunted for the time being remains deenergized to prevent the extension of the start circuit through to the next link in the group.

After the necessary interval has elapsed slow relay 522 releases and in so doing opens thecircuitof relays 516 and 517. .Relay 517 opens the circuit of relay 523 which releases and o ens the original operating circuit througi the winding of relay 509 and the winding of magnet 510. Thereupon, relay 509 operates in series with the magnet 510 in the substitute holding circuit. Relay 517 opens the circuit of the vertical operating magnet 529 and also the circuit of the vertical operating magnet 531.

These two magnets release and restore the associated rods to their normal positions. The connection is now held solely by the maintained energization of the horizon-' tal magnet 510.

At the time the sender selector switch opcrates, another circuit is completed from the grounded conductor 540, through contacts of the switch 500 by way of link 505, conductor 541, winding of relay 102 to battery. The relay 102 operates and extends the tip and ring conductors of the incoming trunk 100 through the sender selector switch 500 to the selected idle sender. Relay 102 opens the circuit of relay 104 which releases. Relay 107, however, is now held in a circuit through its winding to ground at the outer left front contact of relay 102.

The relay 601 which is included in the circuit of conductor 540 for holding the magnet 510 and the relays 509 and 102 operated after the actuation of the sender selector also becomes energized. The relay 601 closes a circuit for relay 602 and this latter relay operates and locks through its make before break contact, conductor 640 toground at the middle right contact of relay 605. The trunk 100 is now extended to the selected idle sender and an impulse circuit is traceable as follows: over the tip conductor of the trunk 100, outer right front contact of relay 102, conductor 116, through contacts of the selector 500, conductor 542, right normal contact of relay 606, conductor 641, windings of relays 634, 633 and 627, conductor 642, left normal contacts of relay 606, conductor 543, contacts of the switch 500, conductor 117, inner right front contact of relay 102, and thence over the ring side of the trunk 100 to the mechanical switching oflice.

At the distant mechanical switching oflice illustrated at the left of Fig. 1 there is shown diagrammatically a selector switch 110 by means of which the connection has been extended to the trunk 100 leading to the term at g ffi e. Moreover there is sh n in diagram a sender 111 and a marker 112 for controlling the switches in the originating ofiice. The sender 111 after having cooperated with the marker 112 to extend the connection to the trunk 100 may further become effective to transmit codes of impulses from the mechanical ofiice over the trunk 100 to the sender at the incoming office for the purpose of setting up a record on the registers shown in Figs. 7 and 8. Fora more detailed description of the method in which the switches at the distant mechanical office may be positioned and the method in which the code impulses are created and transmitted.

from said trunk serve as a, signal to the me-- chanical oflice that the apparatus at the incoming oifice is in condition to receive the code impulses from the sender mechanism 111. Hence the equipment is in condition for transmittingcode impulses over the line circuit for setting the registers in Figs. 7 and 8.

The code impulses are sent over a full metallic circuit comprising both the tip and ring side of the line in series. pulses may be of either positive or negative polarities dependent upon the pole of battery that is connected to a given side of the line circuit. They may also be weak or strong dependent upon whether a high or low resistance is included in the circuit. The relay 634 at the incoming oifice is polarized in such a manner as to respond only when current of ositive polarity flows over'the ring side ot the line; that is, over the conductor 543 and conductor 642. The relay 633 is polarized in such a manner as to respond to current of the opposite polarity. Both relays 634 and 633 respond to strong or weak impulses provided the polarity is proper. Relay 627 responds to strong impulses of either'positive or negative polarity,

but being marginal will not operate on weak impulses.

Since the number of-the called subscribers line is 1 3 2 6, the sender 111 at the distant Voflice transmits a number of codes of impulses representing this number. For the rst digit 1 it transmits a code as follows: first a weak positive impulse, second a weak negative impulse, third no impulse and fourth a weak negative impulse. The second digit 3 is represented by a weak positive impulse, a heavy negative impulse, no impulse, and a weak negative impulse. The third digit 2 is represented by a code beginning with no impulse and followed by a heavy negative impulse, then by a period These imis represented by a weak positive impu "e, a

weak negative impulse, no impulse and a strong negative impulse. The manner in which these impulses are created and transmitted isiillly explained inthe patent to S. B. Williams No. 1,517,331.

In response to the first which is a weak positive impulse, the polarized relay 634 operates and relays 633 and 627 remain inert. Relay 634 completes a circuit from ground through the outer right contact of relay 605, conductor 643, contact of relay 634, left back contact of relay 635, left back contact of relay 703, winding of register relay 711 to battery. Relay 711 operates and locks to the grounded conductor 643. Relay 633 responds to the next impulse which is negative and a circuit is closed from ground over conductor 643 through the contact of relay 633, left back contact of relay 636, left-hand winding of relay 635, left-hand winding of relay 636 to battery. Relay 635 operates in this circuit but relay 636 being marginal does not become energized. Relay 635 c0mpletes a circuit from battery through the left-hand winding of 'rela 636, left-hand .winding'of relay 635, rig t-hand winding of relay 636, inner right contact of rela 635 to grounded conductor 643. Although the right-hand winding of relay 636 is in eluded in this circuit, it is shunted by the circuit previously traced and, therefore, relay 636 still remains deenergized. Relay 635, in operating, completes a circuit from ground over conductor 643, outer right contact of relay 635, outer left back contact of relay 702, winding of relay 703 to battery.

Relay 703 operates and closes a circuit from battery through its winding and the winding of relay 702, inner right front contact of relay 703 to the grounded conductor 643. Relay 702, however, is shunted-by the circuit above traced through the contact of relay 635 and remains deenergized. At the end of the second impulse, relay 633 releases and in so doing removes the shunt from around the winding of relay 636 and this relay operates in series with relay 635. In response to the next and last impulse representing the first digit which is a negative impulse, the relay 633 operates and connects ground potential directly to the left-hand winding of relay 636. This results in shunting the relay 635 which releases its armatures. Relay 635 opens the shunt around the winding of relay 702, but another shunt is maintained around this relay through the inner right contact of relay 636. At the end of the last impulse, relay 633 re leases and opens the circuit of relay 636, whereby relay 702 operates in series with relay 7 03. Thus, for the first digit 1, a code 0? impulses is transmitted resulting in the 

